Implement wxExecute with proper callback on Mac OS X

Backported from head


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@20029 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/spinctrl.h

@@ -100,6 +100,7 @@ protected:
 
     // Handle processing of special keys
     void OnChar(wxKeyEvent& event);
+    void OnSetFocus(wxFocusEvent& event);
 
     // the data for the "buddy" text ctrl
     WXHWND     m_hwndBuddy;